Month: February 2018

Jim Lemon and I have been discussing the most effective and useful visuals to get people out and excited to look for dragonflies. Part of this discussion led to his guest post covering historical flight periods in Ohio. However, those were distribution charts combined for all species of dragonflies and damselflies. They gave you a general idea of the best time to find the most species, but not when x species might be flying. Some of the animated gifs also show the changes in the early or late season flight periods, most likely dependent on weather for that year.

However, I wanted to see if we could have a standardized graph that shows quickly which groups tend to be early season versus late season fliers. Jim Lemon worked his coding magic and was able to create the below graphs for Ohio species. I eventually want to replicate these in R using Ridgeline plots in this new Data Visualization guide (fig 7.9), but I have not had time to experiment with these yet. Below is an additional guest post by Jim Lemon.

-MaLisa Spring

Seeing Relative Species Flight Distribution

We know that individual Odonates only fly for a limited time – typically a number of days to a couple weeks. A few species can be seen flying through most of the season, and so are emerging from their wetland habitat with some regularity. As we record observations, these species data can be counted and plotted against date – and compared to others.

Taking the data for specific groups – Damselflies (Zygoptera), Darners (Aeshnidae), and Skimmers (Libellulidae) – we can plot their flight frequency to see the differences.

Here you can see the average flight period of various damselflies.

If we group by genus and order by increasing numbers we can see the relative flights. Auroras, Sprites, and Red Damsels with relatively low numbers, and peaking early. Jewelwings also peaking relatively early, but in greater numbers. Rubyspots and Spreadwings coming on a little later. Forktails showing their season long records. Finally big numbers for our Bluets and Dancers.

We can also look at individual species of Bluets (Enallagma spp.) to see that there are several species that are mainly found in June (Boreal, Northern, Hagen’s, and Marsh) that are not documented later in the season. We would note that these taxa are also particularly challenging to identify and a good side profile shot of the terminal appendages is needed to differentiate them by photo.

In a similar treatment for the Darners, grouped by genus, we see some flight differences. Again, an early flight for Springtime, Cyrano, Spatterdock, and Swamp. Pretty much full season flight for the Green Darners. Then a late flight for the Spotted and Mosaics, with big numbers for the Mosaic Darners.

The family Libellulidae is a varied group, but we can at least make a flight distribution chart for most of the genera.

The Skimmers are our best represented group in terms of numbers. As a group, they are more consistent – with strong peaks in early-to-mid July. The exceptions on the early side are Whitefaces and Whitetails, on the late side with Meadowhawks and Gliders. If we take two species, Common Whitetail and Autumn Meadowhawk, and segment the data by an arbritrary time period (early years, mid years, recent years) we can get a different view.

Here, we see the early flight of the Common Whitetail and the late flight of the Autumn Meadowhawk. And while there is some variation from period to period, these flight patterns are consistent across years.

Guest post by Jim Lemon

Distribution charts made with data from the Ohio Odonata Society database current as of December 2017. Flight periods reference Ohio flight dates, so expect variation depending on your latitude.

For our survey, it is important to know both where species are present, as well as when they occur. While some species are present through most of the Odonate season, many are limited to specific date periods. To this end, new species flight distribution charts have been created based on current Ohio Odonata Society data. We know these data are not complete, but we work with the information we are provided.

Compiled data from all years of the Ohio Odonata Society Database. Current as of December, 2017.

The Ohio Dragonfly flight period starts in early March and concludes in late November. For our charting, these months are divided into nearly even segments of 1st to the 10th; 11th to the 20th; 21st to month end. Note some months in our target range have 30 days, others 31.

This graph shows all compiled observations prior to 2017 and includes both observation abundances (as much as they are reported) and the number of different species reported on that date.

This graph shows all compiled observations prior to 2017 and includes the observation abundances (as much as they are reported).

This graph shows all compiled observations prior to 2017 and includes the number of different species reported on that date.

The number of recorded observations for each species in the defined periods has been tabulated and used to create the various charts. For any species, you can see the approximate range of flight as well as the periods when most commonly observed. The total number for each period is also displayed. Less common species may tend to have sparse data – but still useful.

This gif shows the change in observations by year. Some years we have many more observations (survey years). Other years you can see a change in flight period with species being observed earlier or later into the season.

This gif is a stacked bar graph which combines all observations to show the main flight period (or main observing period) of dragonflies for Ohio.

We are interested in all of your observations. Observations that document a new record of place or flight – either early or late – is of value in helping understand our Odonates.

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